Ok, I have a 1986 full size, with a 351. Purchased the truck with 51,000 mi, runs great. AC was not functional when I purchased the truck, I charged it up with R-12. Works perfect on an 80 degree day. When temp goes above 90, truck runs on the hot side, (though not totally overheating) and AC does not cool as it should. I do not suspect the fan clutch, as this occours at highway speed as well as when idling. I noticed the truck had a 1 row 1" radiator, so I attempted to replace it with a 2 1/4. Then I find the fan shroud does nto fit, nor does a fan shroud from a later truck with a 2 1/4 radiator. (although they use the the same part # for a 2 1/4 radiator). I have also seen reference stating that an 86 with AC, uses a 1" radiator. Nothing makes sense here! Never heard of an AC vehicle with a 1 row or 1" radiator. Also the radiator HAD previously been replaced. Any ideas?

 

Check fan clutch first. Dead cold, you should only get about one full revolution out of the fan if you spin it by hand. ENGINE OFF PLEASE! Otherwise, there should be enough breeze coming off the fan at idle to stir dust on the roadway below the truck.

Even the smallest radiator in that truck should be a minimum 2-row unit. (It actually may appear as a staggered single row). I know my 93 5.0 (302) had this type in it originally but I immediately swapped in the 4-row unit from my 92 that had been equipped with the Ford OEM tow package. The shroud is definitely a different animal between the two radiators and will be yet another animal if you happen to get one from a truck that was equipped with a 300 (4.9) if I am recalling correctly.

 

I have a '96 EB with the 351L and it came fully loaded from the factory. Last year I began having overheating problems that just wouldn't make sense. I literally replaced everything dealing with the cooling system and, even though things got better, I still had somewhat of a problem. At work one day I was talking with some of our electric substation workers and they showed me the "newest" purchase - a laser temperature measuring device that can be used to take readings on connection points up in the air. I thought about it and tried it out on my truck engine and sure enough things were a bit hotter than I'm comfortable with. As I walked around the front of the truck to get readings from the other side I "shot" the radiator. The first shot was markedly cooler than the engine but the second shot in the lower corner at the hose connection was as hot or hotter! I had replaced the radiator (rebuilt) about two years ago so I hadn't worrried about it causing problems. Sucked it up and got another radiator and - wa-la - the temp gauge barely moves off the lower pin! Now on a Florida summer afternoon I can sit and let the motor run with the a/c blowing full blast and the highest I've been able to get the neeedle is up to the "O" on normal.

It turned out that the older radiator had some "StopLeak" left in it and it had dropped down to the area around the outlet hole - partially blocking it.

 

how does the fan shroud not fit? explain this better if you could please. with out a shroud your not going to get the proper cooling period. I would also take the time to replace your Tstat with a 180* unit since your carbed it wont do anything abnormal. check your timing and give the truck a tune up.

i would for sure run the larger rad

 

New radiator is a good solution. Stop leak is a bad solution, and not really a solution, just a different problem.

 

Ok, So the problem seems to be that the rails on the new radiator were not punched for the pre 87 nose. The shroud sits differently on the radiator. About 10 minuites work with a whitney punch, and the shroud fits perfect. Interesting that the manufacturer claimed it was a proper part, but omitted the necessary holes. (old radiator had same rails, but extra holes. New radiator, needle never goes above center on the temp gauge. Im thinking I will change the fan clutch at some point, just to see if it improves things even more. Would have liked to see the temp lower, but center is not bad im thinking. Thanks all who replied.